can any body tell me how to make this complex object?
The image gives you quite a good blueprint and the first tip is to start with the big forms and then make the details.

Load the blueprint into blender and start modelling with a mirror modifier to model only half of it. 

Start with a Torus and make the bulg on top with a uv sphere that you scaled in x and y to get the desired angle. Connect the two with a boolean -> Union and go on with the other parts in the same way.

For the extrusion part try to model it from the buleprint with single verts and then connect it with the torus to bevel the single verts for a smooth transition.